Method for crimping acrylonitrile polymer fibers



Dec. 22, 1959 'r. c. SPENCE ETAL 2,917,806

METHOD FOR CRIMPING ACRYLONITRILE POLYMER FIBERS Filed June 5. 1957 2 Sheets-Sheet 1 HTTORNEYS 1959 T. c. SPENCE ETAL' 2,917,806

METHOD FOR CRIMPING ACRYLONITRILE POLYMER FIBERS Filed June 5, 1957 2 Sheets-Sheet 2 IN V EN TORS. Thomas 62 Spence Robe/v 6. Funk Harry N Woessn er M MM TTORNZEKS United States METHOD FOR CRIMPKNG ACRYLONITRILE POLYMER FIBERS Application June 5, 1957, Serial No. 663,693

Claims. (Cl. 28-72) This invention has reference to an improved method for crimping fibers, filaments and the like or related shaped articles that consist of and are fabricated from acrylonitrile polymers including, in particular, those that consist entirely of or are based essentially upon polymers that contain at least about 85 percent by weight of acrylonitrile polymerized in their molecules. The invention is especially concerned with an effective method for imparting permanent crimp to acrylonitrile polymer fibers while they are in an aquagel condition. It is primarily intended for practice with fibers and filaments of acrylonitrile polymers that are capable of assuming such a water-swollen or hydrated structure during their prepa ration and which are processed and handled in such form during their manufacture.

For many yarn and fabric constructions and other textile use applications it is desirable in the extreme to impart a wool-resembling or simulating crimp, crinkle, curliness or waviness to fibers and filaments that are comprised of the various man-made artificial and synthetic fiber-forming materials. This sort of physical pattern or formation, as is widely appreciated, lends an interlocking ability and a cohesive quality, as it were, to the fibers. The crimp not only better adapts the fibers for many textile uses, but augments their processing characteristics in and through many textile operations. Fibers and the like that consist entirely of or are based essentially upon acrylonitrile polymer compositions, including polyacrylonitrile, are no exceptions to this desideration. Unfortunately, however, this class or type of synthetic fibers is among the most difficult to crimp with satisfactory measures of success. Not only are they inherently possessed of a relatively low susceptibility to assuming crimpiness, but they are quite noticeably resistant to the permanent retention of any crimp that may, by one or another of the conventional means, he imparted to them.

According to conventional techniques, acrylonitrile polymer fibers (as is frequently the case with other artificial and synthetic filamentary products) are crimped after they have been dried and, usually, while they are already in a permanently heat-set form. While it is known to attempt to directly impart crimp to fibers while they are in such a relatively stable condition, it is a widespread and generally more beneficial practice to crimp the dried fibers while they are in a temporarily swollen or plastified condition. In this way, the fibers are more amenable to assuming the desired alteration of their physical contour. Thus, a suitable and appropriate deforming or crimp-effecting force or means (that usually causes the individual strands of filamentary material to adopt a relatively zig-zag or sinusoidal pattern) is applied while the fibers are under some plastifying influence that tends to diminish their natural resilience and render them more pliable to physical distortion. Dry heat, steam and various solvents and swelling agents have been utilized to exert and achieve the transient plastifying influence and effect. Ordinarily, the deforming means is held or maintained on the fibers that are being crimped until they are atent 0 ice 2,911,806 Patented freed or removed from the plas'tifying influence to which they have been temporarily subjected during theoperation. Or, alternatively, even after being withdrawn from the crimping zone in which the deforming forceor means functions, the fibers are not permitted to be released from the distorted condition to which they have been converted until the plastifying influence has been removed.

One difficulty, among others, is predominantly encountered when acrylonitrile polymer fibers are crimped by any of the known variations of the usual fashion. The fibers are caused to be abnormally stressed during and as a result of the crimping operation. In a large measure, the stresses that have been so derived are found to remain in the crimped fiber. And, invariably, such stresses exert and assert themselves subsequent to the crimping, tending to return the fiber to a less crimp'ed or uncrimped form. This, of course, is inrnilitation with and may defeat the very purpose of the crimping. In addition, it is not uncommon for the known crimping techniques to cause serious physical damage or weakening, or both, of the fibers that have been subjected to the operation.

It would be advantageous, and it is principally among the objects of the invention, to provide an improved method for efiectively and permanently crimping acrylonitrile polymer fibers. It would be of great and pronounced benefit, and it is a singular object of the invention, to secure a type of crimp pattern in the fiber that would be characterized by nicely angled zigzag'gjery to most efficaciously suit the crimped product for the intended purposes. It would also be of advantage, and it is also among the objects of the invention, to provide an improved and effective method for securing a more uni form control over the character of the crimp that is imparted to an acrylonitrile polymer fiber, particularly with respect to consistent uniformity of the crimp pattern and other features correlated thereto. It would he obviously desirable, and it is yet another object of the invention, to achieve the indicated results without occasioning intolerable physical harm in or to the crimped fibers by Way of actual structural damage or undue loss of properties. In this way, the crimped fibers would be imbued with optimum characteristics for their efficient processing through various textile manufacturing and preparatory operations. Likewise, and of at least equal practical significance, they would be well adapted to provide superior and eminently satisfactory yarns, cords, threads and the like filamentary products as well as highly desirable and premium quality cloth and fabric constructed therefrom.

To the attainment of these and corrollary ends, acrylonitrile polymer fibers may advantageously be crimped during their manufacture in which and while they are in an aquagel form and contain an amount of water in the aquagel structure that is at least about equal in weight to the quantity of water-swollen polymer that is in the hydrated structure by a method which comprises applying a closely controlled deforming or crimp-effecting force to the strandular aquagel structure for a very short (almost instantaneous) period of time to impose a zig-zag or serrate crimp pattern in the aquagel fibers; then transferring the so-distorted aquagel fibers in the therebyimposed crimp pattern that they have assumed while they are in a completely unrestrained condition and substantially free from physical extending influences to a drying means; and, finally, drying and dehydrating the crimped aquagel fibers while they are maintained in a completely unrestrained and free-to-shrink condition so as to destroy the aquagel structure and convert it to a utile, crimped and heat-set fiber product.

As has been mentioned, practice of the present is applicable only to and upon strandular, filamentary method and the like aquagel structural forms of fiber-forming polymers that are based upon acrylonitrile. These hydrated forms of the polymer, as is well known, are usually obtained by extruding a spinning solution of the polymer into an aqueous coagulating bath wherein the spinning solvent in the extruded filamentary structure is replaced with water. Although it is desirable for the amount of water that is in the aquagel to at least gravimetrically equal the hydrated polymer that is contained therein, it may oftentimes be preferable for the water to polymer weight ratio in the aquagel to be in the neighborhood of from about 1.5:1, to 2.0:1, respectively. Aquagel structures in which the Water to polymer ratio is as high as2.5 :1 may be satisfactorily processed and crimped in the process of the invention. Advantageously, the aquagel structure may be derived by the extrusion into and coagulation in an aqueous spin bath of a solution of the acrylonitrile polymer that is dissolved in an aqueous saline solvent therefor, such as an aqueous 60 percent by weight zinc chloride solution.

The acrylonitrile polymer fibers that are crimped in the practice of the invention may be the usual homopolymer or copolymer compositions that are adapted to provide the variety of filamentary products that are conventionally referred to as being acrylic fibers. Or, the basic acrylonitrile polymer composition may contain or have other beneficial additament ingredients incorporated therein. These may be the typical pigments, delusterants, textile assistants and the like or they may be dye-assisting adjuvant materials. Thus, minor proportions of certain dye-receptive vinyl lactam polymers, such as polyvinylpyrrolidone, may be incorporated in a polyacrylonitrile or other acrylonitrile polymer aquagel fiber that is to be crimped in accordance with the method of the present invention. It is generally preferred for purposes of terminological classification to characterize the latter, highly advantageous variety of dye-receptive fibers as being nitrile alloy fibers in order to clearly distinguish them from the conventional prototype acrylic fibers that were first known to the art.

Any of the known crimp-effecting means and contrivances that are commonly employed for the purpose may be utilized to provide the deforming force upon the fibers in the practice of the invention. Thus, the conventional stufiing box variety of crimping apparatus may be utilized as may gear crimpers, serrated belt crimpers and the like or equivalent devices. Regardless of the mechanism that is used, however, it is essential that the deforming force that is applied to effect the crimp pattern in the aquagel fiber be between about 50 and 1,000 pounds per square inch of fiber cross-section and that its application during the physical crimp-inducing distortion of the fibers persist for a period of time that is no longer than about five seconds. It is generally of greatest advantage for the deforming force to be maintained in a range that does not exceed about 250 pounds per square inch. If the minimum crimp-inducing force is not employed, there is great likelihood that an inadequately crimped product will be obtained. If the maximum force indi cated is exceeded, it is quite probable that the crimped product will exhibit undesirable irregularity in the crimp cycle and contain a large proportion of extremely sharp and distorted bends. The fiber structure in the area of such severe bends may be physically disrupted and the overcrimped product may exhibit such a reduction in: tensile strength and like diminution of other properties as to become relatively undesirable. Likewise, excessive residence times under the influence of the aquagel deform force may damage the fiber even when the crimp pattern is induced in the fiber within the mentioned range of pressures.

Thus, due to the considerable delicacy of the aquagel structure, great care must be taken in the employment of the crimping apparatus. The temperature of the operatron is relatively immaterial; room temperatures, for eX- ample, being ordinarily suitable.

However, the crimping device must not be operated in such a manner as would permit it to exert the much greater crimping forces that are usual in the conventional techniques relied upon for crimping dried or merely plastified but already heat-set fibers. Frequently, in the common crimping operations that are performed on. dried .fibers,,deforming forces as great as 10,000 to 30,000 pounds or more per square inch of fiber cross-section are encountered. These ponderous forces must be assidously avoided in the practice of the present crimping method on aquagel fibers.

It is ordinarily of greatest benefit to crimp the aquagel fibers after they have been washed (to the greatest desired and practical extent) free of residual spinning solvent and oriented by stretch drawing operations either before, after or during the washing. It is generally expedient to handle the fibers during their spinning and processing and through the crimping operation while they are in continuous filament form and arranged in a bundle or tow of assembled filaments. Such a tow bundle may advantageously have a relatively thin and fiat, rectangular cross-section so as to have a tape or ribbon like configuration. Aquagel fibers that are arranged in a ribbon-like tow bundle are oftentimes found to be best suited for being crimped in accordance with the method of the invention. Flat tows generally facilitate the most efiicient and uniform application of the crimp-inducing deforming force by any of the varieties of crimping ap paratus that may be employed. In. general, when fiat tow bundles are being crimped which are comprised of individual aquagel filaments that will have ultimate dried sizes up to about 15 denier, it is preferable for the average thickness of the tow to be from about ten to forty thousandths of an inch. While its width may vary with the plurality of filaments in the tow, it is usually better for it to be at least about half an inch or so wide. Tows in widths up to four or more inches may be handled with ease.

Most advantageously, the crimping apparatus that is employed in the practice of the invention is an improved. and especially adapted modification of a stutfing box type of crimper which is in general accordance with that which has been disclosed by Thomas C. Spence and Robert B. Funk in their copending application for United States Letters Patent covering Crimping Fibers and having Serial Number 663,764, which was concurrently filed on June 5, 1957. In such an apparatus, the

preferably flat tow bundle of filaments is passed between the bight of an opposed pair of driven nip or feed rollers which discharge and force them into a crimping zone which is defined by and confined within a stufling box of peculiar and highly effective arrangement. The feed rolls of the apparatus are devised and operated to exert only a minimum conveying force on the aquagel filament bundle so as to continuously advance the tow into the stufiing box without tending to crush or deleteriously compress the tender aquagel filaments being handled. The spacing between the opposed filament conveying roll surfaces to exert such a controlled bight should be in the neighborhood of about -90 percent of the average thickness of the fiat aquagel tow. Thus, when the tow thicknesses are within the indicated range, the feed rolls are set with a bight clearance or spacing, proportional to the thickness of the tow, of from about eight to thirty six thousands of an inch. A bight effected in this manner is generally found to be on the order of only about one-tenth or, more frequently, as little as only onehundredth, or so of the compressive force that is exerted by feed rolls in conventional stufiing box crimpers when they are operated in the usual manner on dried fibers.

The aquagel tow being forced into the crimping zone within the stuffing box folds over upon itself in a generally accordion pleat or zig zag pattern while forming a packed column of filaments. This, of course, is due aerasoe to the resistance to the passage of the packed column that is developed in the stuffing box of the crimper. Preferably, such resistance is primarily and substantially completely in the form of an end thrusting or stopping physi- .cal restraint on the packed column that is created at and by the outlet gate or exit valve of the stuffing box against the exodus of the packed column from the crimper. It is most desirable for little or none of the restraint to be caused by the frictional resistance of the side walls of the stufiing box on the packed column passing through the crimper. The pitch or linear frequency of the crimp in the individual filaments depends to a great extent upon the deforming or withholding force that is exerted on the packed column of filaments in the crimping zone within the stuffing box. Of course, as is apparent and known, the amplitude and pitch of the crimp that is induced in the individual fibers is generally much reduced from and relatively unrelated to the accordion fold pattern that is assumed by the packed column of tow in the stuffing box. The stufling box design of the crimper that is disclosed in the referred-to copending application is such as to readily achieve the desired deforming force on the filaments being crimped and to retain them under such critical force deforming conditions for only the requisite crimp-inducing period of time. The stuffing box of such a crimper is expediently capable of the desired accomplishment with minimized and practically negligible frictional resistance on the packed column of crimped tow during its passage through and residence within the crimper.

After it has been crimped and withdrawn from the crimp-inducing means or apparatus that is employed, the tow of aquagel filaments has relatively little crimp permanence. It must be carefully transported or conveyed to and through the drying means with negligible physical restraint or extending influence being permitted to prevail thereon. In addition, the crimped aquagel must be dried in a completely unrestrained and free-to-shrink condition to avoid loss in crimp or other damage to the fiber during the drying operation in which the aquagel is transformed to a strong and useful heat set filamentary product. Ordinarily, the aquagel may be dried most satisfactorily at temperatures between about 100 and 150 C. for periods of time between about thirty and five minutes. Advantageously, for such purposes, the drying means that is employed may be a heated zone or drying oven through which the crimped aquagel is conducted on an endless traveling belt or the like. In this way, the crimped aquagel, after it has been obtained from the crimper, can be gently deposited by suitable means on the belt in such a manner as will avoid disruption of the crimp pattern that has been induced in the aquagel or physical damage of the soft and delicate filaments themselves. The crimped aquagel filaments in repose on the belt are completely unrestrained and free to shrink while passing through the drying oven wherein they are dried and simultaneously heat set to the desired filamentary product. If desired, the crimped aquagel tow can be cut into staple lengths before being dried using suitable cutting means for the purpose. However, when a staple fiber product is required, it is generally preferable to perform the cutting operation on the crimped filaments after they have been dried and heat set.

Practice of the present method provides a superior crimped acrylonitrile polymer fiber product that has a truly permanent degree of crimp retentiveness as a salient and most advantageous characteristic. Any desired degree of crimp can be eifected in the fiber product by the method of the invention. Thus, depending on the time and force combinations employed in the crimping operation or upon particular characteristics of the crimping apparatus that is utilized, relatively coarse or fine crimp can be eflfected. It is not difficult, for example, when a finely crimped product is desired, to impart a permanent crimp in the fiber that has a pitch as fine as 15 :to 20 or so crimps per linear inch of fiber, as may be measured on the =unextended filamentary product.

The invention is further illustrated in and by the following examples wherein, unless otherwise indicated, all parts and percentages are to be taken by weight, which examples are to be considered in connection with the schematic representations of the hereto annexed drawing, in which:

Figure 1 is a diagrammatic portrayal of one embodimen-t in which the method of the invention may be practiced; and

Figures 2 through 9, inclusive, are greatly enlarged depictions of crimp in individual filamentary products, some of which are indicative of results obtained by and in practices other than that which would be in accordance with the invention. 1

Example 1 Using apparatus similar to that schematically delineated in Figure l of the accompanying drawing, and with initial reference thereto, a polyacrylonitrile spinning solution, contained in a suitable supply tank 1, was prepared by dissolving about one part of the polymer having an average molecular weight between about thirty and thirtyfive thousand in about ten parts of a 60 percent aqueous solution of zinc chloride. The spinning solution had a viscosity of about 2,200 poises at a temperature of about 25 C. It was passed from the supply tank 1 through a conduit 2 and forwarded by a metering pump 3, connected therewith, through amass tube 4 having a spinnerette system 5 attached at its termination. About fifteen thousand separate, individually round jet holes were employed in the spinnerette system 5 through which the spinning solution was extruded. The diameter of each jet hole was about 6 mils. The extruded spinning solution was coagulated into a plurality of individual aquagel filaments in a coagulating liquid 6, contained in atrough 7, which was comprised of about a 43 percent aqueous solution of zinc chloride. The spinning solution was extruded at a temperature of about 30 C. and the coagulating bath 6 was maintained at a temperature of about 15 C. during the spinning. The aquagel filaments were passed around the submerged guide 8 in the coagulating liquid and were then withdrawn from the trough 7 through the guide means 9 in the form of a multiple filament tow bundle T. The wet spun tow was then passed about the submerged guides 10 into a distilled water wash bath 11, contained in trough 12, wherein it was washed to the point at which the zinc chloride content of the aquagel filaments was not in excess of about 0.05 percent. The washed tow was then oriented by being stretched to a total length of about twelve times its original length. This was accomplished after the tow was withdrawn from the wash bath on a series of stretch drawing rollers 13 which were operated at sequentially increased peripheral speeds. By these operations there was obtained a washedand oriented filamentary tow bundle of the fifteen thousand individual aquagel strands. The total aquagel denier of the washed and oriented tow bundle was about one-hundred-thousand. The individual aquagel strands in the washed and oriented tow bundle were arranged in aflat, ribbon-like array having a width of about one inch and an average thickness of about twenty thousandths of an inch. The oriented aquagel structures contained about 2.0 parts of water for each part of fiber-forming polyacrylonitrile that was present therein.

The flat tow was then passed over a guide (or guides) 14 and f ed at a rate of about.200 linear feet per minute into the feed rolls 16 and 17 of a stufing box type of crimper, indicated generally by the reference numeral 15, that was similar in design, operation and function to that which is illustrated in and described in connection with the fifth figure in the drawing of the referred to copending application. The feed rolls 16, 17, which were positively driven and rotated in opposite directions so as to-convey and force the tow into the stuffing box 18 of thecrimper, which were about four inches in diameter and which had tow engaging faces of about one inch thick,

other to form the compressive bight on the tow, were prevented by a stop from forming a tow clearance of less than about eighteen thousandths of an inch. Thus. 'the compressive force that was actually exerted on the tow was about 20 pounds. The dimensions of the stufiing box 18, which was of the straight through variety, were such that the residence time of the fibers in the crimper was about 3 seconds with about a four pound restraining weight on the outlet gate of the stufiing box holding the packed column of crimped aquagel fibers in the crimper. The crimping operation was performed with the aquagel filaments atabout room temperature. After being withdrawn from the crimper, the individual crimped filaments in the crimped aquagel tow K (which had been transformed in the operation from the'tow T) had an average pitch of about 5.8 crimps per linear inch of unextended aquagel fiber.

The crimped aquagel tow K was passed through gentlehandling guide means 19 to be deposited on a moving belt 20 which passed through a drying oven 21 which was maintained at a temperature of about 140 C. The crimped aquagel tow K was completely unrestrained and free to shrink on the surface of the belt 20 during its passage through the oven 21 which required about ten minutes. During this drying period, the quagel structure of the crimped filaments in the tow was destroyed to produce dry, 3 denier crimped fibers that had an average pitch of about 8.5 crimps per linear, unextended inch and an average crimp amplitude (measured as the average fiber) of about 0.04 inch.

The dried crimped tow K was passed through a guide 22 to be fed to suitable cutting apparatus 23 wherein it was severed into staple length fibers S which were collected in a storage bin 24. The product crimped staple fibers S exhibited excellent properties for crimped products. For example, their average tensile strength was about 3.7 grams per denier as compared to a strength of a similar uncrimped polyacrylonitrile fiber, prepared in the same manner, or" about 4.0 grams per denier. In addition, when the crimped staple fibers were transformed into webs and slivers during the manufacture of various textile products, their cohesiveness was entirely satisfactory. In addition, the crimp in the fibers was permanently retained, even when subject to boiling water. The desirable crimp pattern that had been permanently imparted to the fibers is illustrated in Figures 2 through of the accompanying drawing. The crimp pattern of a single fiber F as may be obtained in the practice of the invention is shown in Figure 2 as it would appear under greatly enlarged microscopic examination. The uniform angular pattern of the crimp is evident in the fiber which is physically undamaged in its structure. Such a crimp pattern possibilitates the optimum desirable cohesive properties that are obtained in a mass of fibers crimped in accordance with the invention and is indicative of some of the reasons which are believed to be responsible for the crimped fiber retaining substantially all of the desirable physical properties that might be obtained in a similar, but not crimped, acrylonitrile polymer fiber. The bends A of the magnified crimped filaments-in Figures 3, 4 and 5 further illustrate the nice, sharp, undamaged pattern of bending that is achieved in crimped fiber products manufactured by the present method.

Example 11 The procedure of Example I was essentially repeated with the exception that the restraining force employed on the outlet gate of the crimper stufiing box was only ab'outon'e pound. The finally dried crimped fiber product had an average crimppitch of about 5 crimps per linear inch and an amplitude'of about 0.06 inch. Although slightly less so than the product of the first example, the crimped fibers had a crimp pattern imparted to them that had pronounced angularity and desirable uniformity. The crimped fiber product had very desirable properties and was found to process quite well during its conversion from staple form into various textile articles.

In contrast with the foregoing, a polyacrylonitrile fiber tow was prepared as in Example I excepting that it was dried without. being crimped. Instead, it was crimped in tow form as a dried fiber in an embodiment of the conventional manner by being slightly plasticized by heat and then passed through a stufling box crimper which was operated in the usual fashion. The feed rolls of the crimper were thus compressed upon the tow being con veyed to the stuffing box with a bight-providing force of about thirty thousand pounds per square inch of tow cross-section in the rolls. The restraining gate on the stuffing box exerted a deforming force of about six thousand pounds per square inch of tow being crimped. The crimped fibers obtained in this manner were not completely satisfactory, even though about 8 linear crimps per inch had been obtained in the dry crimped product. Their overall crimp pattern in each individual crimped filament exhibited a typical, smoothly-undulating and sinusoidal configuration as is shown by the crimped filament S in Figure 9. This sort of crimp pattern does not secure optimum cohesiveness for a mass of sic-crimped fibers since the individual filaments, due to their noninterlocking configurations, can easily slip past one another when such a crimped fiber mass is being physically processed in a textile operation. In addition, when the fibers that had beencrirnped dry and not in accordance with the present invention were immersed in hot water they lost a good part (about percent) of their crimp. Exposure of the so-crirnped fibers to boiling watercaused them to lose allof their crimp pattern for all practical intents and purposes.

By way of further contrast with the foregoing practice of the invention, when an aquagel tow similar to that employed in the first two examples was directly crimped without being dried in a conventional stuffing box crimper using conventionally high deforming forces in the operation, the resulting crimped fibers were found to be physically damaged and excessively distorted. Under the microscope the bent portions of the so-crimped fibers appeared similar to the bends X in the fibers that are shown in Figures 6, 7, and 8 of the drawing. The tensile strength of the conventionally crimped aquagel fibers was found, upon drying to a finished fiber form, to be less than 1 gram per denier.

Excellent results may also be obtained when crimp-inducing forces and means other than stufiing box crimpers are employed in the practice of the invention.

The scope and purview of the invention is to be gauged in the light of the hereto appended claims rather than strictly from the docent embodiments that have been set forth in the foregoing description and specification.

What is claimed is: V

1. Methodfor crimping synthetic textile fibers based upon acrylonitrile polymers which comprises formingan aquagel filamentary structure of said polymer that con tains an amount by weight of water that is at least about equal to the quantity of polymer in the hydrated structure; crimping the aquagel filamentary structure by de forming it into a crimp pattern under the influence of a force that is between about 50 and 1,000 pounds per square inch of aquagel cross section, said forcebeing applied for a period of time not longer than about five seconds to induce said crimp pattern in the individual filaments in said aquagel structure; transferring the crimped aquagel filamentary structure in an unrestrained condition to a drying means; and drying the crimped aquagel filamentary structure by said drying means while it is in an unrestrained and free-to-shrink condition to destroy the aquagel and convert it to a crimped and heatset fiber product.

2. The method of claim 1, wherein the aquagel filamentary structure is formed with a weight ratio of water to polymer therein that is at least about 1.5 :1, respectively.

3. The method of claim 1, wherein the aquagel filamentary structure is formed as a multiple filament tow bundle prior to being crimped.

4. The method of claim 1, wherein the aquagel filamentary structure is formed as a relatively fiat, ribbonlike multiple filament tow bundle prior to being crimped and is crimped while in the form of said tow by being forced through the crimping zone of a stufiing box type of crimper wherein said deforming force is applied to said aquagel filamentary structure.

5. The method of claim 1, wherein the aquagel filamentary structure is formed as a relatively flat ribhon-like multiple filament tow bundle prior to being crimped that has an average thickness of from about ten to forty thousandths of an inch and is crimped while in the form of said tow by being passed into and forced from between the bight of a pair of conveying feed rolls, having a clearance that is at least about 80-90 percent of the average thickness of the tow, through the crimping 10 zone of a smiling box type of crimper wherein said deforming force is applied to said aquagel filamentary structure.

6. The method of claim 1, wherein the drying means for the crimped aquagel filamentary structure is a heated zone through which the crimped aquagel structure is conveyed and dried in an unrestrained and free-to-shrink condition.

7. A method in accordance with the method set forth in claim 6, wherein the heated zone for drying the aquagel is at a temperature between about and C.

8. The method of claim 1 and including the additional steps of washing and orienting the aquagel prior to said crimping.

9. The method of claim 1, wherein the fibers are based upon polyacrylonitrile.

10. The method of claim 1, wherein the deforming force is maintained between about 50 and 250 pounds per square inch.

References Cited in the file of this patent UNITED STATES PATENTS 2,311,174 Hitt Feb. 16, 1943 2,558,733 Cresswell et a1. July 3, 1951 2,686,339 Holt Aug. 17, 1954 2,811,770 Young Nov. 5, 1957 2,814,837 Stewart et al. Dec. 3, 1957 

1. METHOD FOR CRIMPING SYNTHETIC TEXTILE FIBERS BASES UPON ACRYLONITRILE POLYMERS WHICH COMPRISES FORMING AN AQUAGEL FILAMENTARY STRUCTURE OF SAID POLYMER THAT CONTAINS AN AMOUNT BY WEIGHT OF WATER THAT IS AT LEAST ABOUT EQUAL TO THE QUANTITY OF POLYMER IN THE HYDRATED STRUCTURE; CRIMPING THE AQUAGEL FILAMENTARY STRUCTURE BY DEFORMING IT INTO A CRIMP PATTERN UNDER THE INFLUENCE OF A FORCE THAT IS BETWEEN ABOUT 50 AND 1,000 POUNDS PER SQUARE INCH OF AQUAGEL CROSS SECTION, SAID FORCE BEING APPLIED FOR A PERIOD OF TIME NOT LONGER THAN ABOUT FIVE SECONDS TO INDUCE SAID CRIMP PATTERN IN THE INDIVIDUAL FILAMENTS IN SAID AQUAGEL STRUCTURE; TRANSFERRING THE CRIMPED AQUAGEL FILAMENTARY STRUCTURE IN AN UNRESTRAINED CONDITIONED TO A DRYING MEANS; AND DRYING THE CRIMPED AQUA- 